Performance of various models in structural characterization of n -butanol: Molecular dynamics and X-ray scattering studies

Abstract

Abstract In this work the accuracy of the theoretical predictions for the structure of liquid n-butanol resulting from the model calculations implemented by various force fields is estimated. For this purpose extensive molecular dynamic (MD) simulations of model alcohol were performed applying the Gromacs software package and the following force fields: GROMOS96-54a7, CHARMM27, OPLS-AA, AMBER03, and TraPPE-UA. Utilizing the Complemented system approach method developed for the calculation of X-ray scattering from simulation data [A. Lajovic, M. Tomsic, A. Jamnik, J. Chem. Phys. 133 (2010) 174123] small- and wide-angle X-ray scattering (SWAXS) intensities of model n-butanol resulting from MD simulations were calculated and compared to the experimental scattering data. Since SWAXS is directly sensitive to the molecular structure and the spatial organization of molecules in the scattering media, such comparison represents a stringent test for the quality of the performance of these models in structural characterization of the chosen sample system. The simulation results show that all the tested models reproduce the basic characteristics of the experimental SWAXS curves of n-butanol. However, minor qualitative to considerable quantitative discrepancies in the shape of the scattering functions referring to different force fields are still observed and assigned to different model parametrizations. Simulation results are presented and discussed via the radial and spatial distribution functions and through the H-bonding data.